Supervisor.Spec.supervisor

You're seeing just the function supervisor, go back to Supervisor.Spec module for more information.

supervisor(module, args, options \\ [])

This function is deprecated. Use the new child specifications outlined in the Supervisor module instead.

supervisor(module(), [term()],
  restart: restart(),
  shutdown: shutdown(),
  id: term(),
  function: atom(),
  modules: modules()
) :: spec()

Defines the given module as a supervisor which will be started with the given arguments.

supervisor(module, [], restart: :permanent)

By default, the function start_link is invoked on the given module. Overall, the default values for the options are:

[
  id: module,
  function: :start_link,
  restart: :permanent,
  shutdown: :infinity,
  modules: [module]
]

See the "Supervisor and worker options" section in the Supervisor.Spec module for more information on the available options.